The goal of this project is to use new advances in cryo-electron microscopy (cryo-EM) technology to elucidate the structures of, at high-resolution, a range of functional states of ionotropic glutamate receptor (iGluR) ion channels, and to use complementary functional and biochemical assays to validate our findings and hypotheses driven by our solved cryo-EM models. iGluRs are responsible for the majority of excitatory neurotransmission, and are implicated in a wide range of pathologies, from neurodegenerative diseases and psychiatric disorders, to epilepsy and stroke-induced trauma. Current design of therapeutics targeting the range of iGluR functional states that dictate these different disease states is hindered by a lack of information describing iGluRs outside of a closed-channel state. This research will directly address the need for new views into these functional states by using cryo-EM based methods, which will allow crystallographic barriers in analyzing iGluR states to be overcome. Using state-of-the-art cryo-EM techniques, high-resolution cryo-EM of iGluRs will be established. With fluorescence-based construct screening strategies, new targets for isolating separate structural states in iGluR function will be identified. Namely, how auxiliary proteins interact with/regulate iGluRs and iGluR gating will be targeted. After cryo-EM analysis, data will be probed using advanced electrophysiological techniques and biochemical interrogation. The methods used in this project will serve as a foundation for investigating functional states across ion channel families, and may provide a much-needed template for structure-based drug design of new molecules targeting iGluR states.